Overexpression of a novel soybean gene modulating Na+ and K+ transport enhances salt tolerance in transgenic tobacco plants.

Salt is an important factor affecting the growth and development of soybean in saline soil. In this study, a novel soybean gene encoding a transporter (GmHKT1) was identified and its function analyzed using transgenic plants. GmHKT1 encoded a protein of 419 amino acids, with a potential molecular mass of 47.06 kDa and a predicted pI value of 8.59. Comparison of the genomic and cDNA sequences of GmHKT1 identified no intron. The deduced amino acid sequence of GmHKT1 showed 38-49% identity with other plant HKT-like sequences. RT-PCR analysis showed that the expression of GmHKT1 was upregulated by salt stress (150 mM NaCl) in roots and leaves but not in stems. Overexpression of GmHKT1 significantly enhanced the tolerance of transgenic tobacco plants to salt stress, compared with non-transgenic plants. To investigate the role of GmHKT1 in K(+) and Na(+) transport, we compared K(+) and Na(+) accumulation in roots and shoots of wild-type and transgenic tobacco plants. The results suggested that GmHKT1 is a transporter that affected K(+) and Na(+) transport in roots and shoots, and regulated Na(+) /K(+) homeostasis in these organs. Our findings suggest that GmHKT1 plays an important role in response to salt stress and would be useful in engineering crop plants for enhanced tolerance to salt stress.